U.S. patent application number 11/648632 was filed with the patent office on 2007-05-17 for heat sink with increased cooling capacity and semiconductor device comprising the hear sink.
This patent application is currently assigned to FUJITSU LIMITED. Invention is credited to Ryuuji Miyazaki, Masumi Suzuki.
Application Number | 20070107872 11/648632 |
Document ID | / |
Family ID | 11738133 |
Filed Date | 2007-05-17 |
United States Patent
Application |
20070107872 |
Kind Code |
A1 |
Miyazaki; Ryuuji ; et
al. |
May 17, 2007 |
Heat sink with increased cooling capacity and semiconductor device
comprising the hear sink
Abstract
A heat sink for a semiconductor device comprises a base which
has a first surface on which a plurality of heat-radiating fins are
arranged, and a second surface which contacts the semiconductor
device directly. A heat spreader is provided on the second surface
of the base so that the heat spreader does not contact the
semiconductor device directly.
Inventors: |
Miyazaki; Ryuuji; (Kawasaki,
JP) ; Suzuki; Masumi; (Kawasaki, JP) |
Correspondence
Address: |
ARMSTRONG, KRATZ, QUINTOS, HANSON & BROOKS, LLP
1725 K STREET, NW
SUITE 1000
WASHINGTON
DC
20006
US
|
Assignee: |
FUJITSU LIMITED
Kawasaki
JP
|
Family ID: |
11738133 |
Appl. No.: |
11/648632 |
Filed: |
January 3, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10500464 |
Jul 14, 2004 |
|
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11648632 |
Jan 3, 2007 |
|
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PCT/JP02/00243 |
Jan 16, 2002 |
|
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|
10500464 |
Jul 14, 2004 |
|
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Current U.S.
Class: |
165/80.3 ;
165/185; 257/E23.102; 257/E23.109; 361/705 |
Current CPC
Class: |
H01L 23/367 20130101;
H01L 2924/0002 20130101; H01L 23/3736 20130101; H01L 2924/0002
20130101; H01L 2924/00 20130101 |
Class at
Publication: |
165/080.3 ;
361/705; 165/185 |
International
Class: |
H05K 7/20 20060101
H05K007/20 |
Claims
1. A heat sink for a semiconductor device, comprising: a base
formed of a metallic material having a first surface on which a
plurality of heat-radiating fins are arranged, and a second surface
arranged to contact a semiconductor device directly; and a heat
spreader formed of a metallic material which has a heat
conductivity higher than that of the metallic material of the base
provided on the second surface of the base arranged such that the
heat spreader does not contact a semiconductor device directly when
a semiconductor device is in contact with the second surface.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional application of U.S. Ser.
No. 10/500,464, filed Jul. 14, 2004, which was a U.S. continuation
application filed under 35 USC 111(a) and claims the benefit of
priority under 35 USC 120 and 365(c) from the prior International
Application No. PCT/JP02/00243, filed on Jan. 16, 2002.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a heat sink with increased
cooling capacity, and a semiconductor device comprising the heat
sink with increased cooling capacity.
[0004] 2. Description of the Related Art
[0005] In recent years, in addition to the miniaturization and slim
structure of semiconductor devices such as LSI, there is a growing
demand for increasing the cooling capacity of the heat sink
provided in the semiconductor device, in order to meet the increase
in the heating quantity of LSI.
[0006] In order to effectively dissipate the heat from the
heat-producing semiconductor component such as an LSI chip, the
heat sink usually includes a base in which a plurality of
heat-radiating fins are arranged in parallel formation, and a heat
spreader bonded to the surface of the semiconductor component. For
example, Japanese Laid-Open Patent Application No. 07-273256
discloses such heat sink. The heat spreader is formed of a
thermally conductive metallic material, such as copper. The
heat-radiating fins of the base are provided to receive the heat
generated by the LSI at the time of operation through the heat
spreader and the base, so that the heat received from the LSI is
dissipated in the heat-radiating fins. The heat sink provides the
increased cooling capacity in this manner, and makes it possible to
prevent the temperature of the semiconductor device from exceeding
its heat-resistant temperature due to the heat generated at the
time of operation.
[0007] On the other hand, with the trend of higher integration and
higher speed of the semiconductor devices, many LSI chips have the
increasing amount of heat generated during operation. In order to
increase the cooling capacity of the heat sink more for such
semiconductor devices, it is necessary to enlarge the size of the
heat sink.
[0008] However, the size of the heat sink must meet the restriction
requirements in order to develop the composition of the
semiconductor device. Hence, it is difficult for the conventional
heat sink to meet sufficient cooling capacity by improving only the
configuration of the heat sink. For this reason, it is desired to
configure the heat sink that allows the miniaturization and slim
structure of the semiconductor device wherein the size of the heat
sink can be maintained at a level equivalent to the current size
without reducing the cooling capacity of the heat sink for a highly
heat-producing semiconductor device.
[0009] A description will now be given of an example of the
embedded-type conventional heat sink using FIG. 1 and FIG. 2.
[0010] FIG. 1 shows the composition of the conventional heat sink.
FIG. 2 shows the composition of the semiconductor device comprising
the conventional heat sink shown in FIG. 1. In FIG. 2, (A)
indicates the cross-section of the semiconductor device taken along
the one-dot chain line II-II shown in FIG. 1, and (B) indicates the
back surface of the semiconductor device shown in FIG. 1.
[0011] As shown in FIG. 1 and FIG. 2, the conventional heat sink 1
comprises a base 4 on which a plurality of heat-radiating fins 3
are arranged in parallel formation, and a heat spreader 2 which is
bonded to the front surface of the semiconductor device 5.
[0012] The semiconductor device 5 is, for example, a heat-producing
semiconductor component, such as LSI. The base 4 may be formed of a
metallic material, such as aluminium. The heat spreader 2 may be
formed of a metallic material, such as copper, which has a heat
conductivity higher than that of the metallic material of the base
4.
[0013] In the conventional heat sink, by carrying out a
predetermined forming process, the heat spreader 2 made of copper
is embedded in the back surface of the base 4 made of aluminium, so
that the metallic materials are bonded to each other by the metal
junction.
[0014] As shown in FIG. 2, in the case of the conventional heat
sink 1, all the front surface of the heat spreader 2 is brought in
contact with the base 4. The front surface of the semiconductor
device 5 is bonded to the heat spreader 2 by using the adhesion
agent or mechanical junction. Although the semiconductor device 5
generates heat at the time of operation, the heat-radiating fins 3
are provided to receive the heat from the semiconductor device 5
through the heat spreader 2 and the base 4, and the received heat
is dissipated in the heat-radiating fins 3.
[0015] However, there is the limitation in making small the contact
thermal resistance in the interface between the semiconductor
device 5 and the heat spreader 2, and the contact thermal
resistance in the interface between the heat spreader 2 and the
base 4, and in the case of the conventional heat sink, it is
difficult to increase the cooling capacity more than a certain
level.
[0016] Furthermore, in order to efficiently cool the heat-producing
semiconductor device, such as LSI, it is necessary to enlarge the
thickness of the base and the size (especially height) of the heat
sink to some extent. However, the permissible size of the heat sink
is restricted according to the composition required for the
semiconductor device. Therefore, in the case of the conventional
heat sink, it is difficult to increase the cooling capacity for a
highly heat-producing semiconductor device while maintaining the
size of the heat sink at a level equivalent to the current
size.
SUMMARY OF THE INVENTION
[0017] An object of the present invention is to provide a heat sink
with increased cooling capacity in which the above-described
problems are eliminated.
[0018] Another object of the present invention is to provide a
semiconductor device comprising a heat sink which is provided to
increase the cooling capacity for the highly heat-producing
semiconductor device and to allow the lightweight, slim structure
of the semiconductor device.
[0019] The above-mentioned object of the invention is achieved by a
heat sink for a semiconductor device, the heat sink comprising: a
base having a first surface on which a plurality of heat-radiating
fins are arranged, and a second surface which contacts the
semiconductor device directly; and a heat spreader provided on the
second surface of the base so that the heat spreader does not
contact the semiconductor device directly.
[0020] Moreover, the heat sink of the present invention may be
provided so that the heat spreader comprises an opening which
covers at least a periphery of the semiconductor device bonded
directly to the second surface of the base.
[0021] Moreover, the heat sink of the present invention may be
provided so that the heat spreader comprises a plurality of heat
spreader pieces arranged on the second surface of the base to
encircle a periphery of the semiconductor device, the heat spreader
pieces being embedded in the base so that the heat spreader pieces
are flush with a back surface of the base.
[0022] Moreover, the heat sink of the present invention may be
provided so that the heat spreader comprises a pair of heat
spreader pieces each of which is embedded in the base to oppose one
of side surfaces of the semiconductor device, each heat spreader
piece having a depth that is almost the same as a depth of the base
and having tapered portions along side surfaces of the heat
spreader piece.
[0023] Furthermore, the above-mentioned object of the invention is
achieved by a semiconductor device comprising a heat sink, the heat
sink comprising: a base having a first surface on which a plurality
of heat-radiating fins are arranged, and a second surface which
contacts the semiconductor device directly; and a heat spreader
provided on the second surface of the base so that the heat
spreader does not contact the semiconductor device directly.
[0024] According to the heat sink of the present invention, the
height of the heat-radiating fins can be reduced without reducing
the cooling capacity for the highly heat-producing semiconductor
device, such as LSI, and the lightweight, slim structure of the
semiconductor device can be realized. The heat-conduction loss in
the contact region between the heat spreader and the base can be
reduced when compared with the conventional heat sink, and the heat
can be efficiently dissipated in the whole heat-radiating fins of
the heat sink. Therefore, the heat sink of the present invention
can provide an increased cooling capacity for the highly
heat-producing semiconductor device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] Other objects, features and advantages of the present
invention will be apparent from the following detailed description
when read in conjunction with the accompanying drawings.
[0026] FIG. 1 is a diagram showing the composition of a
conventional heat sink.
[0027] FIG. 2 is a diagram for explaining the composition of a
semiconductor device comprising the conventional heat sink shown in
FIG. 1.
[0028] FIG. 3 is a diagram showing the composition of the heat sink
of the present invention.
[0029] FIG. 4 is a diagram for explaining the composition of a
semiconductor device comprising the heat sink shown in FIG. 3.
[0030] FIG. 5 is a diagram for explaining the composition of a
semiconductor device comprising a heat sink in a preferred
embodiment of the invention.
[0031] FIG. 6 is a diagram for explaining the composition of a
semiconductor device comprising a heat sink in another preferred
embodiment of the invention.
[0032] FIG. 7 is a diagram for explaining the composition of a
semiconductor device comprising a heat sink in another preferred
embodiment of the invention.
[0033] FIG. 8 is a diagram for explaining the composition of a
semiconductor device comprising a heat sink in another preferred
embodiment of the invention.
[0034] FIG. 9 is a diagram for explaining the composition of a
semiconductor device comprising a heat sink in another preferred
embodiment of the invention.
[0035] FIG. 10 is a diagram for explaining the composition of a
semiconductor device comprising a heat sink in another preferred
embodiment of the invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0036] A description will now be given of preferred embodiments of
the present invention with reference to the accompanying
drawings.
[0037] In the following, the elements of the heat sink according to
the invention which are essentially the same as corresponding
elements of the above-described conventional heat sink are
designated by the same reference numerals, and a description
thereof will be omitted, for the sake of convenience.
[0038] FIG. 3 shows the composition of the heat sink 10 of the
present invention. FIG. 4 shows the composition of a semiconductor
device comprising the heat sink 10 shown in FIG. 3. In FIG. 4, (A)
indicates the cross-section of the semiconductor device taken along
the one-dot chain line IV-IV shown in FIG. 3, and (B) indicates the
back surface of the semiconductor device.
[0039] As shown in FIG. 3 and FIG. 4, the heat sink 10 of the
present invention comprises the base 4 and a heat spreader 20. The
base 4 has the front surface on which the plurality of
heat-radiating fins 3 are arranged in parallel formation, and the
back surface to which the semiconductor device 5 is bonded
directly.
[0040] The heat spreader 20 is interposed between the
heat-radiating fins 3 of the base 4 and the semiconductor device 5,
and it is embedded in the back surface of the base 4 so that the
heat spreader 20 does not contact the semiconductor device 5
directly. The semiconductor device 5 is, for example, a
heat-producing semiconductor component, such as LSI.
[0041] Similar to the conventional heat sink 1, in the heat sink 10
of the present invention, the base 4 may be formed of a metallic
material, such as aluminium, and the heat spreader 20 may be formed
of a metallic material, such as copper, which has a heat
conductivity higher than that of the metallic material of the base
4.
[0042] In the heat sink 10 shown in FIG. 4, by carrying out an
extrusion-molding process, the heat spreader 20 made of copper is
embedded in the back surface of the base 4 made of aluminium, so
that the metallic materials are bonded to each other by the metal
junction.
[0043] As shown in FIG. 4, in the heat sink 10 of the present
invention, the semiconductor device 5 is bonded directly to the
back surface of the base 4. By forming an opening 20a in the heat
spreader 20 so that the opening 20a encircles at least the
periphery of the semiconductor device 5, the heat spreader 20 does
not contact the semiconductor device 5 directly. The heat spreader
20 is embedded in the back surface of the base 4 such that the
periphery of the semiconductor device 5 is encircled by the opening
20a of the heat spreader 20.
[0044] Therefore, apart from the conventional heat sink 1, the
contact thermal resistance in the interface between the heat
spreader 20 and the central region of the back surface of the base
4 does not occur according to the heat sink 10 of the present
invention. The front surface of the semiconductor device 5 is
bonded directly to the central region of the back surface of the
base 4.
[0045] With the heat sink 10 of the present invention, the
semiconductor device 5 generates heat during operation. The heat
from the semiconductor device 5 tends to transfer to the
heat-radiating fins 3 arranged in the central region of the front
surface of the base 4 through the base 4. Since the contact thermal
resistance in the interface between the heat spreader 20 and the
central region of the back surface of the base 4 does not occur,
the heat from the semiconductor device 5 readily transfers also to
the heat-radiating fins 3 arranged in the circumferential region of
the front surface of the base 4 through the heat spreader 20 made
of the metallic material with a higher temperature conductivity,
and through the base 4.
[0046] In other words, the whole heat-radiating fins 3 of the front
surface of the base 4 can be made to efficiently conduct the heat
generated by the semiconductor device 5, and the heat-conduction
loss in the interface between the heat spreader 20 and the base 4
can be reduced apart from the conventional heat sink 1. Therefore,
the heat sink 10 of the present invention can provide high cooling
capacity for a highly-heat-producing semiconductor device 5.
[0047] In order to explain in what extent the heat sink 10 of the
present invention can increase the cooling capacity in comparison
with the case of the conventional heat sink 1, the following
simulation analyses are performed. A description will be given of
the results of the simulation analyses.
[0048] For the sake of convenience, an LSI chip whose cross section
is square and whose size is 31 mm.times.31 mm is used as the
semiconductor device 5 in the simulation analyses. The results of
the simulation analyses are obtained by computing the cooling
capacity (thermal resistance) of the conventional heat sink 1 of
FIG. 2 and the cooling capacity (thermal resistance) of the heat
sink 10 of FIG. 4, respectively, when this semiconductor device
(the LSI chip) is operated under the same thermal conditions (10
W).
[0049] As the analysis conditions common to both the conventional
heat sink 1 and the heat sink 10, the array of the heat-radiating
fins has the size of 90 mm.times.90 mm.times.60 mm, the ambient
temperature (Ta) of the heat sink is set at 45 degrees C., the heat
sink is placed horizontally, the thickness of the base 4 is 3 mm,
the number of the fins is 30, and the size of the heat spreader is
66 mm.times.66 mm.times.2 mm.
[0050] Moreover, although each of the conventional heat sink 1 of
FIG. 2 and the heat sink 10 of FIG. 4 has the rectangular
cross-section, it is assumed that all of the semiconductor device
5, the conventional heat sink 1, and the heat sink 10 of the
present invention used for the simulation analyses have the square
cross-section.
[0051] Moreover, for the purpose of the simulation analyses, it is
assumed that the conventional heat sink 1 is configured so that the
entire surface of the copper heat spreader 2 is embedded in the
back surface of the base 4, and the semiconductor device 5 (LSI) is
bonded directly to the back surface of the heat spreader 2 as shown
in FIG. 2.
[0052] In the case of the conventional heat sink 1, the analysis
results show that the temperature (junction temperature Tc) in the
bonded area of the heat sink 1 and the LSI, which is computed under
the above-mentioned heating conditions, is about 83.1 degrees C.,
and the computed cooling capacity (thermal resistance) is about 3.8
degrees C./W.
[0053] On the other hand, in the heat sink 10 of the present
invention, the semiconductor device 5 (LSI) is bonded directly to
the back surface of the base 4, the opening 20a which encircles the
periphery of the semiconductor device 5 is provided in the copper
heat spreader 20, and the heat spreader 20 is bonded to the back
surface of the base 4 without contacting the semiconductor device 5
directly as shown in FIG. 4.
[0054] In the case of the heat sink 10 of the present invention,
the analysis results show that the temperature (junction
temperature Tc) in the bonded area of the heat sink 1 and the LSI,
which is computed under the above-mentioned heating conditions, is
about 79.2 degrees C., and the computed cooling capacity (thermal
resistance) is about 3.4 degrees C./W.
[0055] Namely, it is confirmed that, when compared with the
conventional heat sink 1, the cooling capacity in the case of the
heat sink 10 of the present invention is increased about 10%.
[0056] As described above, since an increased cooling capacity can
be provided according to the heat sink 10 of the present invention,
when the miniaturization and slim structure of the semiconductor
device are required, the height of the fins can be made smaller
than the height of the fins (Ho indicated in FIG. 2) of the
conventional heat sink 1.
[0057] Namely, since the heat sink 10 of the present invention can
provide an increased cooling capacity even when the length of the
heat sink in the width direction is expanded to some extent, it is
possible to make the height of the fins smaller than that of the
conventional heat sink 1, and therefore the miniaturization and
slim structure of the semiconductor device 5 can be realized.
[0058] As shown in FIG. 4, according to the heat sink 10 of the
present invention, even when it is formed so that the base 4 has a
width (W indicated in FIG. 4) larger than the width (Wo indicated
in FIG. 2) of the conventional heat sink 1, the cooling capacity
for the highly-heat-producing semiconductor devices, such as LSI,
is not reduced significantly. Therefore, it is possible to
constitute the heat sink 10 which has the height of the fins (H
indicated in FIG. 4) smaller than the height of the fins (Ho
indicated in FIG. 2) of the conventional heat sink 1. Hence, the
miniaturization and slim structure of the semiconductor device 5
can be realized.
[0059] Next, FIG. 5 shows the composition of a semiconductor device
comprising a heat sink in a preferred embodiment of the
invention.
[0060] Similar to FIG. 4, the heat sink 10A of this embodiment
comprises the base 4 and the heat spreader 20. The base 4 has the
front surface on which the plurality of heat-radiating fins 3 are
arranged in parallel formation, and has the back surface to which
the semiconductor device 5 is bonded directly.
[0061] The heat spreader 20 is interposed between the
heat-radiating fins 3 of the base 4 and the semiconductor device 5,
and it is embedded in the back surface of the base 4 so that the
heat spreader 20 does not contact the semiconductor device 5
directly.
[0062] As shown in FIG. 5, the heat spreader 20 of this embodiment
is provided in elliptical formation, and the heat spreader 20 has a
sufficiently large width (which is the length in the direction of
the major axis) so as to cover the whole heat-radiating fins 3 of
the base 4.
[0063] Moreover, the heat spreader 20 of this embodiment is
provided to have an elliptical opening 20a which encircles the
periphery of the semiconductor device 5. The heat spreader 20 is
embedded in the back surface of the base 4 so that the bottom of
the heat spreader 20 is flush with the back surface of the base
4.
[0064] In the case of the heat sink 10A of this embodiment, when
forming the groove of the base 4 in which the heat spreader 20 is
embedded, the extrusion process or the die-casting process is
performed. When it is formed through the extrusion process, it is
necessary to additionally perform cutting or machining as a
post-processing.
[0065] According to the heat sink 10A of this embodiment, the
height of the heat-radiating fins can be reduced without reducing
the cooling capacity for a highly heat-producing semiconductor
device, such as LSI, and the lightweight, slim structure of the
semiconductor device can be realized.
[0066] Moreover, the heat can be efficiently dissipated in the
whole heat-radiating fins of the heat sink 10A with the heat
spreader 20 of this embodiment, and a high cooling capacity can be
provided for the highly heat-producing semiconductor device.
[0067] FIG. 6 shows the composition of a semiconductor device
comprising a heat sink in another preferred embodiment of the
invention.
[0068] Similar to FIG. 4, the heat sink 10B of this embodiment
comprises the base 4 and the heat spreader 20. The base 4 has the
front surface on which the plurality of heat-radiating fins 3 are
arranged in parallel formation, and has the back surface to which
the semiconductor device 5 is bonded directly.
[0069] The heat spreader 20 is interposed between the
heat-radiating fins 3 of the base 4 and the semiconductor device 5,
and it is embedded in the back surface of the base 4 so that the
heat spreader 20 does not contact the semiconductor device 5
directly.
[0070] As shown in FIG. 6, the heat spreader 20 of this embodiment
is provided in rectangular formation, and the heat spreader 20 has
a sufficiently large width so as to cover the whole heat-radiating
fins 3 of the base 4.
[0071] Moreover, the heat spreader 20 of this embodiment is
provided to have an opening 20a in the shape of a rectangle which
encircles the periphery of the semiconductor device 5. The heat
spreader 20 is embedded in the back surface of the base 4 so that
the bottom of the heat spreader 20 is flush with the back surface
of the base 4.
[0072] In the case of the heat sink 10B of this embodiment, when
forming the groove of the base 4 in which the heat spreader 20 is
embedded, the extrusion process or the die-casting process is
performed. When it is formed through the extrusion process, it is
necessary to additionally perform cutting or machining as a
post-processing.
[0073] According to the heat sink 10B of this embodiment, the
height of the heat-radiating fins can be reduced without reducing
the cooling capacity for a highly heat-producing semiconductor
device, such as LSI, and the lightweight, slim structure of the
semiconductor device can be realized.
[0074] Moreover, the heat can be efficiently dissipated in the
whole heat-radiating fins of the heat sink with the heat spreader
20 of this embodiment, and a high cooling capacity can be provided
for the highly heat-producing semiconductor device.
[0075] FIG. 7 shows the composition of a semiconductor device
comprising the heat sink in another preferred embodiment of the
invention.
[0076] Similar to FIG. 4, the heat sink 10C of this embodiment
comprises the base 4 and the heat spreader 20. The base 4 has the
front surface on which the plurality of heat-radiating fins 3 are
arranged in parallel formation, and has the back surface to which
the semiconductor device 5 is bonded directly.
[0077] The heat spreader 20 is interposed between the
heat-radiating fins 3 of the base 4 and the semiconductor device 5,
and it is bonded to the back surface of the base 4 so that the heat
spreader 20 does not contact the semiconductor device 5
directly.
[0078] As shown in FIG. 7, the heat sink 10C of this embodiment is
the attachment type heat sink. The opening 20a which encircles the
periphery of the semiconductor device 5 is provided in the central
region of the heat spreader 20, and the heat spreader 20 is bonded
in the state where it is attached to the back surface of the base
4.
[0079] The heat spreader 20 is provided with the opening 20a and it
does not contact the semiconductor device 5 directly. The heat
spreader 20 has a sufficiently large width so as to cover the whole
heat-radiating fins 3 of the base 4 and it is interposed between
the heat-radiating fins 3 of the base 4 and the semiconductor
device 5. Therefore, the heat generated by the semiconductor device
5 can be efficiently dissipated in the whole heat-radiating fins 3
of the base 4.
[0080] According to the heat sink 10C of this embodiment, the
height of the heat-radiating fins can be reduced without reducing
the cooling capacity for a highly heat-producing semiconductor
device, such as LSI, and the lightweight, slim structure of the
semiconductor device can be realized.
[0081] Moreover, the heat can be efficiently dissipated in the
whole heat-radiating fins of the heat sink with the heat spreader
20 of this embodiment, and a high cooling capacity can be provided
for the highly heat-producing semiconductor device.
[0082] FIG. 8 shows the composition of a semiconductor device
comprising a heat sink in another preferred embodiment of the
invention.
[0083] Similar to FIG. 4, the heat sink 10D of this embodiment
comprises the base 4 and the heat spreader 20. The base 4 has the
front surface on which the plurality of heat-radiating fins 3 are
arranged in parallel formation, and has the back surface to which
the semiconductor device 5 is bonded directly.
[0084] The heat spreader 20 is interposed between the
heat-radiating fins 3 of the base 4 and the semiconductor device 5,
and it is embedded in the back surface of the base 4 so that the
heat spreader 20 does not contact the semiconductor device 5
directly.
[0085] As shown in FIG. 8, the heat spreader 20 of this embodiment
comprises the four heat spreader pieces which are arranged on the
back surface of the base 4 to encircle the periphery of the
semiconductor device 5, and they are embedded in the base 4 so that
the bottom of these heat spreader pieces 20 is flush with the back
surface of the base 4. The portion of the back surface of the base
4 surrounded by the four heat spreader pieces 20 serves as the
opening 20a.
[0086] In the case of the heat sink 10D of this embodiment, when
forming the groove of the base 4 in which the heat spreader is
embedded, the extrusion process or the die-casting process is
performed. When it is formed through the extrusion process, it is
necessary to additionally perform cutting or machining as a
post-processing.
[0087] According to the heat sink 10D of this embodiment, the
height of the heat-radiating fins can be reduced without reducing
the cooling capacity for a highly heat-producing semiconductor
device, such as LSI, and the lightweight, slim structure of the
semiconductor device can be realized.
[0088] Moreover, the heat can be efficiently dissipated in the
whole heat-radiating fins of the heat sink with the heat spreader
20 of this embodiment, and a high cooling capacity can be provided
for the highly heat-producing semiconductor device.
[0089] FIG. 9 shows the composition of a semiconductor device
comprising a heat sink in another preferred embodiment of the
invention.
[0090] Similar to FIG. 4, the heat sink 10E of this embodiment
comprises the base 4 and the heat spreader 20. The base 4 has the
front surface on which the plurality of heat-radiating fins 3 are
arranged in parallel formation, and has the back surface to which
the semiconductor device 5 is bonded directly.
[0091] The heat spreader 20 is interposed between the
heat-radiating fins 3 of the base 4 and the semiconductor device 5,
and it is embedded in the back surface of the base 4 so that the
heat spreader 20 does not contact the semiconductor device 5
directly.
[0092] As shown in FIG. 9, the heat spreader 20 of this embodiment
comprises a pair of heat spreader pieces each of which is embedded
in the base 4 to oppose one of the side surfaces of the
semiconductor device 5, and each heat spreader piece 20 having a
depth that is almost the same as a depth (B indicated in FIG. 9
(B)) of the base 4. The portion of the back surface of the base 4
surrounded by the heat spreader pieces 20 of this embodiment serves
as the opening 20a.
[0093] In the case of the heat sink 10E of this embodiment, when
forming the groove of the base 4 in which the heat spreader 20 is
embedded, it is possible to perform only the extrusion process. It
is not necessary to additionally perform cutting or machining as a
post-processing which is needed for the previously described
embodiments.
[0094] On the other hand, in the case of the conventional heat sink
using the embedded type heat spreader, after the heat spreader is
embedded in the base of the conventional heat sink, it is necessary
to additionally perform the post-processing (for example, cutting,
machining or the like) on the base in order to obtain a sufficient
level of parallelism.
[0095] However, according to the heat sink 10E of this embodiment,
performing such post-processing is unnecessary, and therefore the
heat sink 10E of this embodiment is useful for reduction of the
manufacturing cost.
[0096] FIG. 10 shows the composition of a semiconductor device
comprising a heat sink in another preferred embodiment of the
invention.
[0097] Similar to FIG. 4, the heat sink 10F of this embodiment
comprises the base 4 and the heat spreader 20. The base 4 has the
front surface on which the plurality of heat-radiating fins 3 are
arranged in parallel formation, and has the back surface to which
the semiconductor device 5 is bonded directly.
[0098] The heat spreader 20 is interposed between the
heat-radiating fins 3 of the base 4 and the semiconductor device 5,
and it is embedded in the back surface of the base 4 so that the
heat spreader 20 does not contact the semiconductor device 5
directly.
[0099] As shown in FIG. 10, the heat spreader 20 of this embodiment
comprises a pair of heat spreader pieces each of which is embedded
in the base 4 to oppose one of the side surfaces of the
semiconductor device 5, each heat spreader piece 20 having a depth
that is almost the same as a depth (B indicated in FIG. 10 (B)) of
the base 4, and each heat spreader piece 20 having tapered portions
along the side surfaces of the heat spreader piece 20.
[0100] The portion of the back surface of the base 4 surrounded by
the heat spreader pieces 20 of this embodiment serves as the
opening 20a. Each heat spreader piece 20 having the tapered
portions is provided so that the heat spreader piece has a varying
width that gradually decreases in the downward direction. Namely,
because of the tapered portions, the width of each heat spreader
piece 20 at the top thereof is the maximum width, and the width of
each heat spreader piece 20 at the bottom thereof is the minimum
width as shown in FIG. 10 (A).
[0101] Moreover, in the case of the heat sink 10F of this
embodiment, when forming the groove of the base 4 in which the heat
spreader 20 is embedded, it is possible to perform only the
extrusion process. It is not necessary to additionally perform
cutting or machining as a post-processing which is needed for the
previously described embodiments.
[0102] Furthermore, in the case of the heat sink 10F of this
embodiment, the tapered portions, which make the width of the heat
spreader gradually decrease in the downward direction, are formed
on the side surfaces of each heat spreader piece 20, and it is
possible to prevent separation of the heat spreader pieces 20 from
the base 4 even when a special bonding process is not performed
after the heat spreader pieces 20 are fitted in the grooves of the
base 4. Therefore, performing the post-processing and performing
the special bonding process are unnecessary, and the heat sink 10F
of this embodiment is more useful for reduction of the
manufacturing cost.
[0103] The present invention is not limited to the above-described
embodiments, and variations and modifications may be made without
departing from the scope of the present invention.
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